Dental materials include porcelain facings, veneers, porcelain bridges, porcelain inlays, ceramic jacket crowns, all ceramic crowns, and a multitude of other porcelain dental products. Dental ceramics are typically fired in an inert environment such as in a vacuum atmosphere. Bottom loading furnaces can be used to heat treat the materials whereby the material to be heat treated is set on the lower shelf and is raised to an upper heating chamber for the heating process. Alternatively, a furnace, such as a pressing furnace, may have a stationary bottom shelf for placement of the material to be heat treated which may include the step of pressing the material into a desired form. In this type of furnace, the heating chamber is lowered over the material and the heating process commences. Although bottom-loading furnaces tend to have more uniform heating within the heating chamber than front loading furnaces, which experience cold spots at the front of the unit, nonuniform heating may still occur. The placement of the piece to be treated on the lower unheated insulation block may result in the occurrence of cool spots or insufficient predrying of the piece. As a result, longer soak times are required to heat the pressing mold and/or firing plate. Moreover, if the temperature distribution is uneven, workpieces treated in the same lot will be subject to variation in quality.
There remains a need to reduce cold spots in the furnace and provide uniform heating throughout the heating chamber of the furnace. It is desirable to provide a furnace for heating dental materials having a uniform heating atmosphere without compromising the efficiency and operation of the furnace.